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clicking from main board on a panasonic TX-42AS650B smart tv

Discussion in 'Troubleshooting and Repair' started by RICHARD GRAY, Jan 11, 2018.

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  1. RICHARD GRAY

    RICHARD GRAY

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    Jan 11, 2018
    HI, i am trying to repair a TX-42AS650B i have replaced the power board, main board and t con board but it has not resolved the problem that i started out with that is "i have got back lights but no sound and no picture?" i have a clicking sound coming from the main board. i have done all that i can think of as i am new to tv repair. could anyone please advice me on maybe what this problem could be?, reguards richard.
     
  2. kellys_eye

    kellys_eye

    4,275
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    Jun 25, 2010
    Can you see a picture - use a torch and look at the screen from a sharp angle. If the backlight isn't working you can, if you're careful, still see the picture.

    Either way, the clicking is from the over-current protection circuitry (the power supply constantly tries to 'start' but is shut down due to a fault condition elsewhere).

    Start by removing the power cables from the individual boards in the set - see if you can identify which cable stops the clicking.

    If you have LED backlighting then a shorted LED is common. Repair requires dismantling of the screen - sometimes accessible from the back of the TV, other times requiring the removal of the actual LCD panel - a sphincter-rattling experience.

    The LED will be part of a strip of them - one or more will require replacement. They are 'keyed' (left/right) so you need to order the right bit. They are, fortunately, simple plug-in units but, as mentioned, getting the screen apart is often the hardest part.
     
  3. RICHARD GRAY

    RICHARD GRAY

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    Jan 11, 2018
    Thank you for getting back to me. i tried the torch test the other day and could not see anything on the screen, i am going to try the power cable thing today. if one of the leads stops the clicking then do i change that lead? where the LEDs are concerned is it going to be obvious that the LEDs are blown or is there a common sign to look out for? thank you for your time.
     
  4. RICHARD GRAY

    RICHARD GRAY

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    Jan 11, 2018
    EFDBE547-F184-41CC-8789-D3B3A44C23E4.jpeg View attachment 38543 if one
     
  5. RICHARD GRAY

    RICHARD GRAY

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    Jan 11, 2018

    Attached Files:

  6. HellasTechn

    HellasTechn

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    Apr 14, 2013
    I recommend that you get a digital multi meter and set it to diode test, then check all diodes you can see on the PSU.

    You may by chance locate a shorted diode that triggers the protection. If not then you have wasted 5 minutes of your time. :)
     
  7. RICHARD GRAY

    RICHARD GRAY

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    Jan 11, 2018
    I think that you might be right about it being an LED because the clicking stops when this lead is out from the t con. I’m going in deep today i feel like I might be getting somewhere thank you
    i have found my problem the display is knackeredif I can find a replacement screen for the right price I’ll will go for it. Cheers for your comments regards richard
     

    Attached Files:

  8. kellys_eye

    kellys_eye

    4,275
    1,146
    Jun 25, 2010
    Man, that is some fault! Never seen that part of a display go off in the fashion before!
     
    RICHARD GRAY likes this.
  9. RICHARD GRAY

    RICHARD GRAY

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    Jan 11, 2018
    Tell me about itI’ve spent hours looking on line for display buffer/inverter boards. I have seen some very close but not the ones. I figure if I can find them or it if they don’t come in pairs it would be a result
     
  10. 73's de Edd

    73's de Edd

    2,939
    1,246
    Aug 21, 2015
    Sir Richard Gray . . . . . .

    QUESTION . . .? dependent upon your visual inspection

    in looking at your final 3rd photo, with the images closeup limitation.
    That appears to be spider webbing build up on the best amassed clump of it.
    In the black areas one would immediately associate that with carbonized burn up.
    With your inspection, could that instead be an amassed black mold transition from humidity
    presence on the webbing.
    If that is the case instead; that goo would be conductive across circuitry.
    AS far as the LOW voltage level used in that area I would NOT expect it to be able to burn
    a board to a carbonized state.

    Can you confirm this units blackened areas ?

    I believe that all of that blackening might clean off with denatured alcohol, as well take care of the
    "webs ? ".
    A POSITIVE NO-NO is to attempt to do that clean up with the unit in its present position.
    The unit needs to be inverted top to bottom such that the ribbon cable will the be positioned well above the
    area to be cleaned, and no alcohol nor black residue will ever reach up, or wick up to the edge of the ribbon cable.
    .
    If this then cleans up, and you then get the board bone dry your problem may have then just been IMPERMISSIBLE conductivity between components covered with the conductive black death.
    What say ye ?

    73's de Edd

    ....
     
  11. RICHARD GRAY

    RICHARD GRAY

    9
    0
    Jan 11, 2018
    Definitely
     
    Last edited by a moderator: Jan 12, 2018
  12. RICHARD GRAY

    RICHARD GRAY

    9
    0
    Jan 11, 2018
    I can’t see any spiders webs LOL
     
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